but parents in one contra county city are being put on alert because the game can be danger. rob roth is live with the rule of engagement that are putting kids at risk. >> reporter: high school students call the competition assassins. they divide into teams and shoot nerf guns at each other. but school officials say it's gotten out of hand. this you tube video from a san ramon high school student gives you an idea of the nerf gun assassins competition. but officials from the unified school district send an e-mail to high school students saying the competition may be getting dangerous and is not sanctioned by the school district. >> and they're getting in their cars and they're speeding through traffic and they're chasing each other and those kind of things. that's just dangerous behavior. >> reporter: officials say some students are dressing in black ninja style clothes and painting their guns black. yesterday sheriff deputies received an alarmed call from an elementary school not knowing it was a game. >> a teacher and there were a few young students around too. saw somebody